It is known that organic materials are damaged by light, radiation, heat or oxygen. There are already numerous documents which describe compounds for stabilizing organic material against said effects. Such compounds are usually free-radical scavengers, hydroperoxide decomposers, quenchers (extinguishers for excited states) or UV absorbers (cf. R. Gachter, H. Muller, Plastics Additives Handbook, 3rd Ed., Hanser Verlag, Munich 1990, p. 133 ff). In connection with UV absorbers, the compounds involved are generally based on 2-hydroxybenzophenone, 2-hydroxyphenylbenzotriazole, cinnamic esters and oxanilides (cf. R. Gachter, H. Muller, Plastics Additives Handbook, 3rd Ed., Hanser Verlag, Munich 1990, p. 181 ff). The class of the o-hydroxy-substituted triphenylpyrimidines can also be regarded as a separate type of UV stabilizer (DE-A4 416 809).
Said classes of compound often have specific disadvantages which occur alongside the desired stabilizing effect. In respect in particular of color characteristics, interaction with pigments, compatibility of different stabilizers with one another and with the material to be stabilized, resistance to chemicals and water (sensitivity to hydrolysis), storage stability, migration behavior and improvement in stabilization to the harmful effects of heat and light, especially in long-term use, there is a great need for new classes of stabilizer.
Derivatives of 4-hydroxyquinoline-3-carboxylic acid of the formula (I) have been known for some time in connection with pharmaceutical applications (cf. e.g. E. Schroetter et al., Pharmazie (1977), 32(4), 223-5).
The applications relate to the action of compounds of the formula (I) against bacteria, parasites, tumors, suppurating ulcers, gastrointestinal dysfunctions and as enzyme inhibitors. Nothing is known of any stabilizing action of compounds of the formula (I) on organic material, especially their potential as UV absorbers.
Processes for preparing compounds of the formula (I) are known, for example, from Organic Syntheses Coll. Vol. III, p. 274; Houben-Weyl, Heterarene II, Part 1, Volume E7a, p. 343 ff.